In many circumstances it would be useful to form a relatively long rigid member from a compact source at one end. For example a robotic arm that can transfer parts through vacuum doors in a multiple chamber vacuum system has proven important in the design of the cluster tools used in the integrated circuit manufacturing industry. In the past such devices have usually used lead screws, pneumatic or hydraulic cylinders, or pantograph type mechanisms to effect their operation. Robotic extension arms are also useful additions to autonomous or remotely controlled robots in a wide range of applications from those used in planetary exploration to those involved in munitions detection and passivation.
Structural extending members comprising three flexible tapes have been described in U.S. Pat. Nos. 4,625,475; 3,242,576; and 5,056,278, all of which are incorporated herein by reference. In U.S. Pat. No. 3,242,576, Wheeler describes a rigid, extendable measurement device in which three flexible metal tapes are held together at their edges by means of hook-and-loop material to form a rigid structure with a triangular cross section. In U.S. Pat. No. 4,625,475, McGinnis describes an extensible mast, which is erected from a portable base. The mast comprises a plurality of tapes reinforced with a wrap material. In U.S. Pat. No. 5,056,278, Atsukawa describes an extensible support pole in which telescoping cylindrical bodies are extended and retracted by means of band-like plates. The band-like plates are held in place within the cylindrical bodies by partition members having guide slits or guide holes to accommodate the band-like plates. None of these disclosures describe retaining rings that are carried on an extendable structure comprising a plurality of tapes.